We have developed quantitative, sensitive assays for the lipid A and O antigen moieties of Gram-negative bacterial endotoxin. In the proposed experiments we want to use these assays to examine several problems: (1) the release of LPS from the bacterial surface (2) whether or not O antigen is released "free" from core or lipid A constituents of LPS; (3) the relationship of capsular polysaccharide content to release of LPS; (4) the activation/degradation of LPS by human plasma; (5) disappearance of LPS from the circulation of experimental animals, and the effect of LPS infusion upon renal blood flow.